Rapid diagnostic kits for the detection of microbial antigens constitute an important tool in the world economy. Some of the major developments with these kits have focussed on inventions that offer a shorter assay time, ease of use, minimal or no requirement for sophisticated equipment, low cost, and versatility for testing both small and large number of samples.
One such assay is an Enzyme Linked Immunosorbent Assay (ELISA). In a classical model of ELISA, specific antibody is coated on a solid phase. This antibody is typically referred to as the `capture antibody`. A test sample containing an antigen is complimentary to the specific antibody is added to the solid phase allowing the antigen to be specifically captured by the antibody immobilized on the solid phase. The non-specific substances in a sample are then removed by simple washing with buffer solutions, Subsequently, an antibody-enzyme conjugate is added which binds to the antigen, or some part of the antigen/antibody complex. After washing away the excess unbound conjugates, an appropriate substrate solution is added so that a colored product (or some other detectable product) is generated and in amounts directly proportional to the antigen present in the test sample. This procedure is well established and well know to those skilled in the art.
The prior art describes a number of solid phases that are coated with a specific antibody in order to capture the antigen in a given test sample. Typically, in order to be able capture the entire amount of the antigen contained in a test sample, a reasonable excess of the antibody has to be coated on the solid phase. For commercial purposes, both polyclonal and monoclonal antibodies are therefore required to be produced in large quantities. Both types of antibodies are relatively expensive to produce. Hence, when large, excess amounts have to be used for coating the solid phase, the cost of the antibody significantly boosts the overall cost of any resulting diagnostic kit or assay. An alternative substance to a `capture` antibody would therefore be a technological innovation and a commercial attraction. There is therefore a need to find a cheaper way to achieve the same type of binding properties as exhibited by such `capture` antibodies.
Traditional solid support used for performing ELISA have been, predominantly polystyrene surfaces such as microtiter plates or test tubes, polyethylene or polycarbonate and nylon, or nitrocellulose membranes. More recently, a hydrophobic synthetic polyester cloth sheet has been utilized as the solid phase. The advantages of such a solid support sheet over the other traditional solid supports has been described elsewhere (B. Blais and H. Yamazaki, Use of a hydrophobic cloth for enzyme immunoassay, Biotechnology Techniques, 3: 23-26, 1989).